This invention pertains to the accurate and precise positioning of loads by an electric step motor system and is related to the system disclosed in my U.S. Pat. No. 3,644,764 and in my prior copending application Ser. No. 657,989 filed Feb. 13, 1976.
Disclosed in my patent and application, referenced above, are a pair of step motors interconnected in series and simultaneously pulsed for stepped advancement of a load to a selected position. The step motor driving the load has a relatively large angle stepping characteristic for rapid advancement of the load toward a final position that is interpolated between large angle steps by the simultaneous drive of the other step motor having a relatively small angle stepping characteristic. It is therefore an important object of the present invention to provide a plural step motor system of the foregoing type wherein both step motors are of the large angle type and nevertheless provide interpolated positioning of a load with comparable accuracy.